Project 2 focuses on two issues. The first is the extent to which major nutritional and genetic factors that alter the probability of intestinal tumor formation in the mouse - individually and in combination - alter the levels and activity of key components of the ?-catenin-Tcf-- c-myc/cyclin D1/cdk4 -- p21/p27 pathway, and its intersections with machinery of the cell cycle. The unique features of this aim are the evaluation of the stoichiometry of the components in vivo, the extent and nature of complex formation in vivo, and the activity of these complexes. This is complemented by the extensive matrix of genetic - dietary factors to be investigated by use of tissue from Project 1. This makes use of 3 mouse genetic models of intestinal cancer developed by us - the Apc1638, Muc2 and Msh2G674S mice - and the nwdiet#1, which is high in fat and phosphate, low in calcium, vitamin D, choline, methionine and folate. This diet induces premalignant changes and tumor formation in wild-type mice, and the contribution of the overall diet, and each of its components, is dissected in Project 1. The second aim is to use both a tissue culture system, as well as the tissue resource from Project 1 (through the Histopathology Core), to pursue our recent work that demonstrates that dietary factors can recruit a block to c-myc transcriptional elongation that circumvents deregulation of the gene due to altered 13-catenin-Tcf signaling. The mechanisms of this block will be investigated, and, utilizing a novel method of imaging of c-mye transcription sites in individual nuclei (Genomics Core), we will determine the extent to which this mechanism is utilized in vivo, how it is recruited by dietary factors in vivo, and whether it also functions in regulation of cyclin D1 expression.